Method of handling MBMS MDT in wireless communication system

ABSTRACT

A method of handling a multimedia broadcast multicast service (MBMS) minimization of driver test (MDT) for a network of a wireless communication system includes transmitting a first MBMS measurement configuration to instruct a first user equipment (UE) to perform an MBMS MDT operation; receiving a first MBMS measurement result and a first multicast-broadcast single frequency network (MBSFN) area identity (ID) which indicates that the first MBMS measurement result is generated for a first MBSFN area identified by the first MBSFN area ID, from the first UE; and processing the first MBMS measurement result according to the first MBSFN area ID.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No.61/926,972, filed on Jan. 14, 2014 and entitled “Method and Apparatusfor handling MBMS MDT logging in a wireless communication system”, thecontents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method utilized in a wirelesscommunication system, and more particularly, to a method for handling amultimedia broadcast multicast service (MBMS) minimization of drivertest (MDT) in a wireless communication system.

2. Description of the Prior Art

A long-term evolution (LTE) system supporting the 3rd GenerationPartnership Project (3GPP) Rel-8 standard and/or the 3GPP Rel-9 standardis developed by the 3GPP as a successor of a universal mobiletelecommunication system (UMTS) for further enhancing performance of theUMTS to satisfy increasing needs of users. The LTE system includes a newradio interface and a new radio network architecture that provide highdata rate, low latency, packet optimization, and improved systemcapacity and coverage. In the LTE system, a radio access network knownas an evolved universal terrestrial radio access network (E-UTRAN)includes multiple evolved Node-Bs (eNBs) for communicating with multipleuser equipments (UEs), and communicating with a core network including amobility management entity (MME), a serving gateway, etc., forNon-Access Stratum (NAS) control.

A LTE-advanced (LTE-A) system, as its name implies, is an evolution ofthe LTE system. The LTE-A system targets faster switching between powerstates, improves performance at the coverage edge of an eNB, andincludes advanced techniques such as carrier aggregation (CA),coordinated multipoint (CoMP) transmission/reception, uplink (UL)multiple-input multiple-output (MIMO), etc. For a UE and an eNB tocommunicate with each other in the LTE-A system, the UE and the eNB mustsupport standards developed for the LTE-A system, such as the 3GPPRel-10 standard or later versions.

Multimedia broadcast multicast service (MBMS) service or evolved MBMS(E-MBMS) service has been introduced in the UMTS, the LTE system and theLTE-A system, for broadcasting multimedia contents such as TV programs,films, music, etc. Compared with the traditional unicast, the MBMSservice (hereafter referred to both the MBMS service and/or the E-MBMSservice) is provided in downlink only, and is broadcasted from thenetwork to multiple (e.g., a specific group of) UEs via apoint-to-multipoint transmission. Characteristic of the MBMS serviceenables the network to provide the MBMS service to unlimited number ofUEs with a constant network load. In addition, a UE in the UMTS, the LTEsystem and/or the LTE-A system may receive the MBMS service inherently,and no additional hardware component is needed to be installed for theMBMS service. Thus, the MBMS service is attractive, considering bothhardware cost and resource efficiency.

Multicast-broadcast single frequency network (MBSFN) is a communicationchannel defined for the MBMS service. In MBSFN transmission, signalsfrom several antennas of potentially different base stations arecombined in the UE. This combination makes MBSFN transmission differentfrom unicast transmission, and makes the performance of MBSFNtransmission difficult to be verified than unicast transmission. MBSFNtransmission is unacknowledged. There is no feedback to the radio accessnetwork (RAN) which broadcasts the MBMS transmission, such as hybridautomatic repeat request (HARQ) or radio link control (RLC)acknowledgements, meaning that the RAN does not know whether the MBSFNtransmissions are successfully received or not. Hence, it is difficultfor an operator to understand the quality of MBMS services beingdelivered. Thus, the only way to verify and optimize MBSFN radiotransmission is to do manual drive test.

Unfortunately, using manual drive tests for network optimizationpurposes is costly, and this contributes in environmental emission ofCO₂ and more importantly, comes with a limitation in measuring placesalong a drive route which is generally not typical to where customersconsume MBMS services.

Minimization of drive test (MDT) functionalities, including logged MDTand immediate MDT, are performed or logged by UEs to collect information(or called measurement logs) in the idle mode or connected mode, andreport the information to the network, to reduce network maintenancecosts for operators, ensure faster optimization cycle resulting inhigher customer satisfaction, and help to reduce the carbon emission toprotect the environment. According to 3GPP specifications, a loggedmeasurement configuration message is utilized for configuring a UE toperform the MDT functionalities. However, it is not clear how to extendthe MDT functionalities to support MBMS MDT function.

SUMMARY OF THE INVENTION

It is therefore an objective of the present invention to provide amethod for handling a multimedia broadcast multicast service (MBMS)minimization of driver test (MDT) in a wireless communication system tosolve the abovementioned problem.

An embodiment of the present invention discloses a method of handling anMBMS MDT for a network of a wireless communication system. The methodcomprises transmitting a first MBMS measurement configuration toinstruct a first user equipment (UE) to perform an MBMS MDT operation;receiving a first MBMS measurement result and a firstmulticast-broadcast single frequency network (MBSFN) area identity (ID)which indicates that the first MBMS measurement result is generated fora first MBSFN area identified by the first MBSFN area ID, from the firstUE; and processing the first MBMS measurement result according to thefirst MBSFN area ID.

An embodiment of the present invention further discloses a method ofhandling an MBMS MDT for a UE of a wireless communication system. Themethod comprises receiving an MBMS measurement configuration comprisingan MBSFN area ID identifying an MBSFN area from a first network; andperforming an MBMS MDT operation for the MBSFN area in response toreception of the MBMS measurement configuration comprising the MBSFNarea ID identifying the MBSFN area.

An embodiment of the present invention further discloses a method ofhandling an MBMS MDT for a UE of a wireless communication system. Themethod comprises receiving an MBMS measurement configuration whichinstructs the UE to perform an MBMS MDT operation, from a first networkof the wireless communication system; performing the MBMS MDT operationfor an MBSFN area where the UE is receiving an MBMS service via an MBSFNtransmission, in response to reception of the MBMS measurementconfiguration; and transmitting an MBMS measurement result generated byperforming the MBMS MDT operation and an MBSFN area ID to a network ofthe wireless communication system, wherein the network is the firstnetwork or a second network of the wireless communication system.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communication systemaccording to an embodiment of the present invention.

FIG. 2 is a schematic diagram of an MBSFN deployment in a wirelesscommunication system.

FIG. 3 is a schematic diagram of a communication device according to anembodiment of the present invention.

FIG. 4 is a flowchart of a process according to an embodiment of thepresent invention.

FIG. 5 is a flowchart of a process according to an embodiment of thepresent invention

DETAILED DESCRIPTION

It is desirable to have automated solutions, to provide the ability fornetwork operators to gather information such as radio measurements whichare associated with customer UEs and use this information to assistnetwork operation and optimization.

Please refer to FIG. 1, which is a schematic diagram of a wirelesscommunication system 10 according to an embodiment of the presentinvention. The wireless communication system 10 is briefly composed of anetwork and a plurality of user equipments (UEs). In FIG. 1, the networkand the UEs are simply utilized for illustrating the structure of thewireless communication system 10. Practically, the network may be auniversal terrestrial radio access network (UTRAN) comprising aplurality of Node-Bs (NBs) in a universal mobile telecommunicationssystem (UMTS). Alternatively, the network may be an evolved UTRAN(E-UTRAN) comprising a plurality of evolved NBs (eNBs) and/or relays ina long term evolution (LTE) system, a LTE-Advanced (LTE-A) system or anevolution of the LTE-A system.

Furthermore, the network may also include both the UTRAN/E-UTRAN and acore network, wherein the core network includes network entities such asMobility Management Entity (MME), Serving Gateway (S-GW), Packet DataNetwork (PDN) Gateway (P-GW), Self-Organizing Networks (SON) server,Radio Network Controller (RNC), multimedia broadcast multicast service(MBMS) gateway, Multi-cell/Multicast Coordination Entity (MCE) and/orOperation and Maintenance (O&M) entity, etc. In other words, after thenetwork receives information transmitted by a UE, the information may beprocessed only by the UTRAN/E-UTRAN and decisions corresponding to theinformation are made at the UTRAN/E-UTRAN. Alternatively, theUTRAN/E-UTRAN may forward the information to the core network, and thedecisions corresponding to the information are made at the core networkafter the core network processes the information. In addition, theinformation may be processed by both the UTRAN/E-UTRAN and the corenetwork, and the decisions are made after coordination and/orcooperation are performed by the UTRAN/E-UTRAN and the core network. AUE may be a mobile phone, a laptop, a tablet computer, an electronicbook or a portable computer system but is not limited. In addition, thenetwork and the UE may be seen as a transmitter or a receiver dependingon the transmission direction, e.g., for an uplink (UL), the UE is thetransmitter and the network is the receiver, and for a downlink (DL),the network is the transmitter and the UE is the receiver. Morespecifically, for the network, the direction of the transmission is DL,and the direction of the reception is UL. For the UE, the direction ofthe transmission is UL, and the direction of the reception is DL.

Please refer to FIG. 2, which is a schematic diagram of amulticast-broadcast single frequency network (MBSFN) deployment in awireless communication system such as the UMTS, the LTE system or theLTE-A system. The wireless communication system supports MBMS, which isa multimedia service performed by MBSFN. In detail, MBMS is apoint-to-multipoint service in which data is transmitted from a singlesource entity to multiple recipients. Transmitting the same data tomultiple recipients allows network resources to be shared. Cellsparticipating in MBSFN transmission should be synchronized tightly intime. According to 3rd Generation Partnership Project (3GPP)specifications, an MBSFN synchronization area refers to an area of thenetwork where all NBs or eNBs can be synchronized and perform MBSFNtransmissions. Therefore, the MBMS service received by a UE may not beinterrupted when the UE moves between different cells within the MBSFNsynchronization area.

In addition, an MBMS service area refers to an area within which data ofa specific MBMS session (or MBMS service) are sent, and an MBSFN area isan area consisting of a group of cells within an MBSFN synchronizationarea, which are coordinated to achieve an MBSFN transmission. In FIG. 2,the MBSFN synchronization area is capable of supporting one or moreMBSFN area. On a given frequency layer, an eNB (or a Node-B) may belongto one or more MBSFN areas. An MBSFN transmission refers to a simulcasttransmission technique realized by transmission of identical waveformsat the same time from multiple cells within an MBSFN area, which may beseen as a single transmission to a UE. That is, the NBs or eNBs in anMBSFN area may transmit the same data (i.e. MBMS) to multiple UEssimultaneously. The UE may only need to consider a subset of the MBSFNareas which are configured, i.e., when the UE knows which MBSFN areaapplies for the service(s) it is interested to receive.

Please refer to FIG. 3, which is a schematic diagram of a communicationdevice 30 according to an embodiment of the present invention. Thecommunication device 30 may be utilized for realizing a UE or thenetwork shown in FIG. 1, but is not limited herein. The communicationdevice 30 may include a processing means 300 such as a microprocessor orApplication Specific Integrated Circuit (ASIC), a storage unit 310 and acommunication interfacing unit 320. The storage unit 310 may be any datastorage device that stores a program code 314, accessed and executed bythe processing means 300. Examples of the storage unit 310 include butare not limited to a subscriber identity module (SIM), read-only memory(ROM), flash memory, random-access memory (RAM), CD-ROM/DVD-ROM,magnetic tape, hard disk and optical data storage device. Thecommunication interfacing unit 320 is preferably a transceiver and isused to transmit and receive signals (e.g., messages or packets)according to processing results of the processing means 300.

Please refer to FIG. 4, which is a flowchart of a process 40 accordingto an embodiment of the present invention. The process 40 may beutilized in a network of the wireless communication system 10, such as aNode-B of a UMTS system or an eNB of a LTE/LTE-A system, with the MBSFNdeployment shown in FIG. 2, for handling MBMS minimization of drive test(MDT) operation. The process 40 may be compiled into the program code314 and includes the following steps:

Step 400: Start.

Step 402: Transmit an MBMS measurement configuration to instruct a UE toperform an MBMS MDT operation.

Step 404: Receive an MBMS measurement result and an MBSFN area identity(ID) which indicates that the MBMS measurement result is generated foran MBSFN area identified by the MBSFN area ID, from the UE.

Step 406: Process the MBMS measurement result according to the MBSFNarea ID.

Step 408: End.

In one embodiment, the network may transmit a first MBMS measurementconfiguration which instructs a first UE to perform an MBMS MDToperation, to the first UE (step 402). After the first UE performs theMBMS MDT operation, the network may receive a first MBMS measurementresult and a first MBSFN area ID which indicates that the first MBMSmeasurement result is generated for a first MBSFN area identified by thefirst MBSFN area ID, from the first UE (step 404), and thus the networkmay process the first MBMS measurement result according to the firstMBSFN area ID (step 406). In the above example, the network transmitsthe first MBMS measurement configuration to the first UE and receivesthe first MBMS measurement result and the first MBSFN area ID from thefirst UE; and in another example, in addition to cooperate with thefirst UE, the network by the process 40 may further transmit a secondMBMS measurement configuration to a second UE (to instruct the second UEto perform the MBMS MDT operation) and receives a second MBMSmeasurement result and a second MBSFN area ID which indicates that thesecond MBMS measurement result is generated for a second MBSFN areaidentified by the second MBSFN area ID, from the second UE, and thenetwork may process the second MBMS measurement result according to thesecond MBSFN area ID. An MBSFN area ID is broadcasted by the network sothe UE receives the MBSFN area ID from the network.

In one embodiment, the network may receive a notification from the UE,notifying that there is an MBMS measurement result stored in the UE, andthe network may transmit a request to the UE to request reporting of theMBMS measurement result stored in the UE.

In one embodiment, the MBMS measurement configuration that the networktransmits may include the MBSFN area ID identifying the MBSFN area whichthe MBMS MDT operation (by the UE) is performed for. In anotherembodiment, the MBMS measurement configuration that the networktransmits may include no MBSFN area ID. No matter whether the MBMSmeasurement configuration includes any MBSFN area ID, the UE maytransmit an MBMS measurement result along with an MBSFN area IDidentifying an MBSFN area which the MBMS MDT operation (by the UE) isperformed for. Hence the network knows the MBMS measurement result isgenerated by the UE according to the MBMS MDT operation performed forthe MBSFN area. The UE may transmit a plurality of MBMS measurementresults and a plurality of MBSFN area IDs, and each of the MBSFN areaIDs identifies an MBSFN area which at least one of the plurality ofMBSFN measurement results is generated for.

Please refer to FIG. 5, which is a flowchart of a process 50 accordingto an embodiment of the present invention. The process 50 may beutilized in a UE of the wireless communication system 10 with the MBSFNdeployment shown in FIG. 2, for handling MBMS MDT operation. In oneembodiment, the UE implemented with the process 50 is capable tocommunicate with a network implemented with the process 40 and receiveMBMS service from the network. The process 50 may be compiled into theprogram code 314 and includes the following steps:

Step 500: Start.

Step 502: Receive an MBMS measurement configuration comprising an MBSFNarea ID identifying an MBSFN area from a network.

Step 504: Perform an MBMS MDT operation for the MBSFN area in responseto reception of the MBMS measurement configuration comprising the MBSFNarea ID identifying the MBSFN area.

Step 506: End.

According to the process 50, the UE may receive an MBMS measurementconfiguration from the network (step 502), wherein the MBMS measurementconfiguration comprises an MBSFN area ID identifying an MBSFN area. Inresponse to reception of the MBMS measurement configuration, the UE mayperform an MBMS MDT operation for the MBSFN area (step 504). MBMS MDToperation can be named different, such as MBSFN logged measurement orany other similar.

More specifically, the step of performing the MBMS MDT operation (step504) for the MBSFN area includes to perform an MBMS measurement for theMBSFN area identified by the MBSFN area ID, for generating an MBMSmeasurement result, and to store the MBMS measurement result, i.e.logging. It should be noted that in general cases, the UE may performthe MBMS measurement for the MBSFN area only if the UE receives the MBMSmeasurement configuration including the MBSFN area ID identifying theMBSFN area and if the UE is receiving the MBMS service provided viaMBSFN transmission, but this condition is not a limit to the embodimentsof the present invention. In another case, the UE may perform the MBMSmeasurement for the MBSFN area as long as the UE receives the MBMSmeasurement configuration including the MBSFN area ID identifying theMBSFN area, regardless of whether the UE is receiving the MBMS servicevia MBSFN transmission or not. In another case, the UE may perform theMBMS measurement as along as the UE receives an MBMS service andgenerates an MBMS measurement result. In this case, the step ofperforming the MBMS MDT operation may include storing the MBMSmeasurement result, i.e. logging.

In one embodiment, after the UE has the stored MBMS measurement result,the UE may further transmit a notification to the network, for notifyingthat there is an MBMS measurement result stored in the UE. The UE mayfurther transmit the stored MBMS measurement result for the MBSFN areato the network after receiving a request from the network. Note that thenetwork that transmits the request may be the same as or different fromthe network that transmits the MBMS measurement configuration to the UE.For example, the UE may receive the MBMS measurement configuration froma first network (e.g., a first eNB), and transmit the MBMS measurementresult to a second network (e.g., a second eNB) which transmits therequest to the UE. In another example, the UE may receive the MBMSmeasurement configuration from the first network and transmit the MBMSmeasurement result to the first network if the first network transmitsthe MBMS measurement configuration and also transmits the request to theUE.

In another embodiment, the UE may transmit not only the stored MBMSmeasurement result corresponding to the MBSFN area where the MBMSmeasurement is performed for, but also the MBSFN area ID identifying theMBSFN area, to the second network (different from the first network thattransmits the MBMS measurement configuration to the UE).

Please note that, the UE may receive the MBMS service via MBSFNtransmission when the UE does not receive MBMS measurement configurationyet, and the UE may perform MBMS measurement anytime when receiving MBMSservice(s). In one embodiment, once the UE receives an MBMS servicebelonging to a first MBSFN area, the UE may perform MBMS measurement forthe first MBSFN area and does not store the MBMS measurement resultuntil the UE receives an MBMS measurement configuration including afirst MBSFN area ID identifying the first MBSFN area. Later, when the UEreceives the MBMS measurement configuration including the first MBSFNarea ID, the UE then stores the MBMS measurement result corresponding tothe first MBSFN area in the storage unit of the UE.

As mentioned above, the UE may perform MBMS measurement anytime whenreceiving MBMS service(s). For example, the network may instruct the UEto perform MBMS measurement and store an MBMS measurement result every10 milliseconds. Alternatively, the network may instruct the UE toperform MBMS measurement for every 5 MBSFN subframes in which the UEreceives the MBMS service(s), and store the average value of themeasurement results of every 5 MBSFN subframes. The UE then transmitsthe stored measurement result to the network.

Please note that the network may configure different MBSFN area IDs fordifferent UEs according to locations of the UEs or MBMS servicessubscribed by the UEs. For example, a first UE may subscribe MBMSservice(s) belonging to a first MBSFN area but not subscribe MBMSservice(s) belonging to a second MBSFN area. A second UE may subscribeMBMS service(s) belonging to the second MBSFN area but not subscribeMBMS service(s) belonging to the first MBSFN area. In such a condition,the network may configure the first UE with a first MBMS measurementconfiguration including a first MBSFN area ID identifying the firstMBSFN area, and configure the second UE with a second MBMS measurementconfiguration including a second MBSFN area ID identifying the secondMBSFN area, where the first MBSFN area ID and the second MBSFN area IDare different.

In a further embodiment, the network may configure a UE with an MBMSmeasurement configuration including more than one MBSFN area ID. The UEmay perform an MBMS MDT operation for each MBSFN area in response to thereception of the MBMS measurement configuration including eachcorresponding MBSFN area ID. More specifically, the UE may perform theMBMS measurement for each MBSFN area identified by the MBSFN area IDsincluded in the MBMS measurement configuration and store the MBMSmeasurement result corresponding to each MBSFN area and the UE maytransmit the stored MBMS measurement results to the network.

The UE may receive MBMS services simultaneously from a first MBSFN areaand a second MBSFN area. In an embodiment, for a condition that the UEmay perform MBMS measurement after the UE receives an MBMS measurementconfiguration including only one MBSFN area ID and the MBSFN area ID iscorresponding to the first MBSFN area, the UE may perform MBMSmeasurement for the first MBSFN area and store the MBMS measurementresult corresponding to the first MBSFN area; the MBMS measurement isnot performed for the second MBSFN area and no MBMS measurement resultcorresponding to the second MBSFN area is generated and stored. In thiscase, the MBMS measurement for the second MBSFN area is regarded as notrequested by the network.

In another embodiment, for a condition that the UE may perform MBMSmeasurement once an MBMS service is received by the UE, the UE mayperform measurement on both of the first MBSFN area and the second MBSFNarea. Later, if the UE receives an MBMS measurement configurationincluding only one MBSFN area ID and the MBSFN area ID is correspondingto the first MBSFN area, the UE may store the MBMS measurement resultcorresponding to the first MBSFN area and not store the MBMS measurementresult corresponding to the second MBSFN area. In other words, the MBMSmeasurement for the second MBSFN area may be still performed, but theMBMS measurement result for the second MBSFN area may be discarded(e.g., not stored in the UE).

In several conditions, when performing an MBSFN transmission, thenetwork may detect how many UEs are receiving the MBSFN transmission. Ifthere are fewer number of UEs receiving the MBSFN transmission, thenetwork may stop the MBSFN transmission and change to apply unicasttransmissions to respective UEs, which allows the network to releaseseveral resources which originally used for MBSFN transmission to beused for general data transmissions. In such a condition, the MBSFNtransmission is changed to a unicast transmission. The network mayinform the UE of this change via the system information. Accordingly,the UE may stop the reception of MBMS service via the MBSFN transmissionand establish a radio resource control (RRC) connection to the networkto receive the MBMS service via the unicast. Note that when the UE stopsreceiving the MBMS service via MBSFN transmission, the UE may stopperforming the MBMS measurement.

In an embodiment, for a condition that the UE may perform an MBMSmeasurement when the UE is receiving an MBMS service belonging to afirst MBSFN area identified by a first MBSFN area ID, as long as the UEstops receiving the MBMS service belonging to the first MBSFN areaidentified by the first MBSFN area ID, the UE may stop performing theMBMS measurement. For example, the UE may stop receiving any MBMSservice(s) belonging to the first MBSFN area, or the UE may change toreceive an MBMS service belonging to a second MBSFN area identified by asecond MBSFN area ID. In such a condition, the UE may stop performingthe MBMS measurement.

Preferably, the UE may store an MBMS measurement result corresponding toan MBSFN area only when the MBMS measurement result for the MBSFN areais requested by the network. In such a condition, the memory of the UEwill be used for the measurement data requested by the network. Incontrast, if all MBMS measurement results for every MBSFN area providingMBMS services are stored by the UE to be reported to the network, agreat amount of memory of the UE may be occupied by the measurement dataeven if several of these measurement data are useless data, resulting inworse performance of the UE.

The MBMS measurement result may be, for example, a measurement log. Ifthere is/are measurement log(s) stored in the memory, the UE may informthe network (e.g., an eNB) of information indicating the existence ofmeasurement log (s) via a RRC message or another uplink message. Afterthe network receives this indication, the network may request the UE toreport the measurement log (s) via another RRC message at a specifictime. The UE then transmits the measurement log(s) to the network.

Please note that the MBMS measurement result may include at least one ofan evolved universal terrestrial radio access (E-UTRA) carrier MBSFNreceived signal strength indicator (RSSI), an MBSFN signal-to-noiseratio (SNR), a reference signal received power (RSRP) of an MBSFNsignal, an MBSFN reference signal received quality (RSRQ) and a blockerror rate (BLER). The format of the MBMS measurement result may beindicated to the UE by the network via the MBMS measurementconfiguration. That is, the network may transmit the MBMS measurementconfiguration to configure the MBMS measurement result in form ofmetrics including at least one of the E-UTRA carrier MBSFN RSSI, theMBSFN SNR, the RSRP of the MBSFN signal, the MBSFN RSRQ and the BLER.For example, if the network makes a request that the UE should reportthe MBMS measurement result in form of RSRP, the UE may report the valueof RSRP accordingly. In general, the format of the MBMS measurementresult stored in the UE may be the same as the format requested by thenetwork, so the UE may report the MBMS measurement result directly. Insome embodiment, the format of the MBMS measurement result stored in theUE may be different from the format requested by the network. Forexample, if the network transmits a request that the UE should reportthe MBMS measurement result in form of RSRP, the UE may store a doubleRSRP value in its memory, and report the RSRP value as the MBMSmeasurement result after dividing the stored value by two.

It should be noted that the UE may not report the MBMS measurementresult to the network immediately after receiving the MBMS measurementconfiguration. Instead, the UE may store the MBMS measurement resultwhen receiving the MBMS measurement configuration, and report the MBMSmeasurement result after receiving the request from the network. Forexample, after the UE receives the MBMS measurement configuration from afirst network and the UE moves from the first network to a secondnetwork before transmitting the MBMS measurement result, the UE thentransmits the MBMS measurement result to the second network.

Furthermore, if the second network obtains the MBMS measurement resultfrom the UE, the second network may not know which MBSFN area the MBMSmeasurement result is used for. In such a condition, the UE may furthertransmit the MBSFN area ID identifying an MBSFN area to the secondnetwork, in order to indicate that the MBMS measurement result isgenerated corresponding to the MBSFN area identified by the MBSFN areaID. The second network either processes the MBMS measurement resultaccording to the MBSFN area ID, or transmits the MBMS measurement resultand the MBSFN area ID to a network entity. The network entity is acentralized node responsible for collecting and processing MBMSmeasurement results from different UEs and may be a standalone node ormay be located in an MCE, an O&M entity or an MME.

If the second network or the network entity does not receive the MBSFNarea ID from the UE, the second network or the network entity may stillprocess the MBMS measurement result and associate the MBMS measurementresult to the MBSFN area ID via a cell global identity of a cell inwhich the UE performs MBMS measurement. The UE may transmit the cellglobal identity to indicate the cell which the MBMS measurement resultis generated from signals measured from. If the cell in which the UEperforms MBMS measurement belongs to only one MBSFN area, the secondnetwork or the network entity may derive the MBSFN area ID of this MBSFNarea from the cell global identity.

For example, the second network or the network entity may have mappinginformation (e.g., a mapping table) between the cell global identity andthe MBSFN area ID. The second network or the network entity may look upthe mapping information to use the cell global identity to find theMBSFN area ID.

When the second network or the network entity gets the MBSFN area IDeither from the UE or derived by itself, the second network or thenetwork entity may process the MBMS measurement results by classifyingand analyzing the MBMS measurement results according to the MBSFN areaID. Based on the analysis, the second network or the network entityoptimizes the MBSFN transmission for the MBSFN area. For example, basedon the analysis, the second network or the network entity may configuremore cells to perform MBSFN transmission to enhance MBMS quality withinan MBSFN area if the signal quality within this MBSFN area is weaker; orthe second network or the network entity may configure fewer cells toperform MBSFN transmission within an MBSFN area if the MBMS qualitywithin this MBSFN area is good enough, in order to save electricitypower. The second network or the network entity may further increaseMBSFN transmission power of a cell for an MBSFN area if the signalquality within this MBSFN area is weaker in the cell; or decrease MBSFNtransmission power of a cell for an MBSFN area if the signal qualitywithin this MBSFN area is good enough in the cell.

Please note that there are some cells belonging to more than two MBSFNareas simultaneously. For each of these cells, at least one subframe ofthe cell may be used for a first MBSFN area, and at least one of othersubframes of the cell may be used for a second MBSFN area. If an MBSFNarea ID included in the MBMS measurement configuration is used for thefirst MBSFN area, the UE may perform the MBMS measurement by measuringthe MBSFN subframe(s) allocated to the first MBSFN area, which isidentified by the MBSFN area ID. If an MBSFN subframe for the firstMBSFN area is specified to be measured, the UE may measure a referencesignal in the MBSFN subframe, to determine the measurement values (e.g.the MBSFN SNR, MBSFN RSSP and/or MBSFN RSSQ) of the first MBSFN area.The MBMS measurement may be performed by the UE in an idle mode or aconnected mode, which should not be a limitation of the presentinvention and should be different from the logged MDT and immediate MDTin the prior art.

Since the network knows that which subframes are used for MBSFNtransmission of the first MBSFN area, the MBMS measurement configurationtransmitted by the network may include a subframe configurationindicating which subframe to be measure. The MBMS measurementconfiguration may further include a channel configuration indicatingwhich channel such as Multicast Control Channel (MCCH) or MulticastTraffic Channel (MTCH) to be measured, and/or an MBMS serviceconfiguration indicating an MBMS service to be measured. The UE mayperform MBMS measurement and store an MBMS measurement result on thechannel according to the channel configuration and/or on subframe(s)where the MBMS service is received according to the MBMS serviceconfiguration. In an embodiment, the network may transmit the MBMSmeasurement configuration to the UE after receiving capabilityinformation from the UE, wherein the capability information indicatesthat the UE supports an MBMS measurement capability. In other words, ifa UE does not support the MBMS measurement capability, the network maynot transmit the MBMS measurement configuration to the UE to instructthe UE to enable the capability to perform the MBMS MDT operation inresponse to receiving the MBMS service. The MBMS measurement capabilitymay be contained in a UE capability information message. The network maytransmit a UE capability enquiry message to the UE, and the UE maytransmit the UE capability information message in response to receptionof the UE capability enquiry message.

Please note that the MBMS measurement configuration may be included in alogged measurement configuration message. In the prior art, the loggedmeasurement configuration message is used for transmitting theconfiguration of logged MDT (which is not MBMS MDT), and the presentinvention may configure the logged measurement configuration message tofurther transmit the MBMS measurement configuration of MBMS MDT. Morespecifically, if the logged measurement configuration message can alsobe used for transmitting the MBMS measurement configuration, the loggedmeasurement configuration message may include MBMS measurementconfiguration which may include an MBSFN area ID. If the MBMSmeasurement configuration does not include any MBSFN area ID, thenetwork will require that the UE performs MBMS measurements on any MBSFNarea where the UE is receiving any MBMS service. The UE stores the MBMSmeasurement results and an MBSFN area ID corresponding to an MBSFN areawhen the UE is receiving any MBMS service in the MBSFN area. The MBMSmeasurement configuration may further include carrier frequencyinformation indicating the carrier frequency on which the UE performs anMBMS measurement.

However, according to 3GPP TS 36.331 v11.6.0, section 5.6.6.3, the UEshall discard the logged measurement configuration as well as the loggedmeasurement information specified in section 5.6.7 upon receiving a newlogged measurement configuration message. This means that the UE maydiscard the logged measurement configuration and the correspondingmeasurement result (or the MBMS measurement configuration and the MBMSmeasurement result) for the logged measurement configuration messagereceived previously when the UE receives a new logged measurementconfiguration message. If a UE is capable of both MBMS MDT and loggedMDT functionalities, the UE should be able to store the MBMS measurementresult and logged MDT measurement result simultaneously. In such acondition, the information element for MBMS measurement configurationshould be exclusive of the information element for logged measurementconfiguration, i.e., LoggedMeasurementConfiguration-r10-IEs, in order toprevent the MBMS measurement result from being discarded when the UEreceives a logged measurement configuration message having theinformation element LoggedMeasurementConfiguration-r10-IEs, or preventthe logged MDT measurement result from being discarded when the UEreceives a logged measurement configuration message having the MBMSmeasurement configuration. For example, a UE may receive a loggedmeasurement configuration message including a logged measurementconfiguration (i.e., LoggedMeasurementConfiguration-r10-IEs) and store alogged MDT measurement result accordingly. Then, if the UE receives alogged measurement configuration message including an MBMS measurementconfiguration (e.g., LoggedMeasurementConfiguration-r12-IEs), the UE maystore the MBMS measurement result without discarding the previouslystored logged MDT measurement result; that is, the UE may store the MBMSmeasurement result and the logged MDT measurement result simultaneously.

Alternatively, the MBMS measurement configuration may be included in aRRC message other than the logged measurement configuration message. Ifthe UE receives a RRC message including the MBMS measurementconfiguration where the RRC message is different from the loggedmeasurement configuration message, the UE may not discard the previouslystored logged MDT measurement result.

Those skilled in the art should readily make combinations, modificationsand/or alterations on the abovementioned description and examples. Theabovementioned steps of the processes including suggested steps can berealized by means that could be a hardware, a firmware known as acombination of a hardware device and computer instructions and data thatreside as read-only software on the hardware device, or an electronicsystem. Examples of hardware can include analog, digital and mixedcircuits known as microcircuit, microchip, or silicon chip. Examples ofthe electronic system can include a system on chip (SOC), system inpackage (SiP), a computer on module (COM), and the communication device30.

To sum up, the present invention provides a method of handling MBMS MDTin a wireless communication system. The method allows the network toconfigure UEs to perform MBMS measurement on specific MBSFN area(s) viathe MBMS measurement configuration. When receiving the MBMS measurementconfiguration, the UE may enable an MBMS MDT operation for the MBSFNarea(s) specified by the network. More specifically, the UE may storethe MBMS measurement result(s) for the MBSFN area (s) specified by thenetwork and then transmit the MBMS measurement result(s) to the network,in order to realize MDT for MBMS services.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A method of handling a multimedia broadcastmulticast service (MBMS) minimization of driver test (MDT) for a networkof a wireless communication system, the method comprising: transmittinga first MBMS measurement configuration to instruct a first userequipment (UE) to perform an MBMS MDT operation after receivingcapability information indicating that the first UE supports an MBMSmeasurement capability from the first UE; receiving a first MBMSmeasurement result and a first multicast-broadcast single frequencynetwork (MBSFN) area identity (ID) which indicates that the first MBMSmeasurement result is generated for a first MBSFN area identified by thefirst MBSFN area ID, from the first UE; and processing the first MBMSmeasurement result according to the first MBSFN area ID.
 2. The methodof claim 1, wherein the first MBMS measurement configuration comprisesthe first MBSFN area ID.
 3. The method of claim 1 further comprising:transmitting a second MBMS measurement configuration to instruct asecond UE to perform the MBMS MDT operation; receiving a second MBMSmeasurement result and a second MBSFN area ID which indicates that thesecond MBMS measurement result is generated for a second MBSFN areaidentified by the second MBSFN area ID, from the second UE; andprocessing the second MBMS measurement result according to the secondMBSFN area ID.
 4. A method of handling a multimedia broadcast multicastservice (MBMS) minimization of driver test (MDT) for a user equipment(UE) of a wireless communication system, the method comprising:receiving an MBMS measurement configuration comprising amulticast-broadcast single frequency network (MBSFN) area identity (ID)identifying an MBSFN area from a first network; and performing an MBMSMDT operation for the MBSFN area in response to reception of the MBMSmeasurement configuration comprising the MBSFN area ID identifying theMBSFN area; wherein the step of performing the MBMS MDT operation forthe MBSFN area in response to reception of the MBMS measurementconfiguration comprising the MBSFN area ID identifying the MBSFN areacomprises: performing an MBMS measurement for the MBSFN area identifiedby the MBSFN area ID for generating an MBMS measurement result; storingthe MBMS measurement result for the MBSFN area identified by the MBSFNarea ID; and transmitting a notification to the first network fornotifying that the UE has the stored MBMS measurement result for theMBSFN area identified by the MBSFN area ID.
 5. The method of claim 4,further comprising: transmitting the stored MBMS measurement result tothe first network or a second network in response to a request sent bythe first network or the second network.
 6. The method of claim 4,further comprising: transmitting the stored MBMS measurement result andthe MBSFN area ID to the first network or a second network in responseto a request sent by the first network or the second network.
 7. Themethod of claim 4, wherein the MBMS measurement result comprises atleast one of an evolved universal terrestrial radio access (E-UTRA)carrier MBSFN received signal strength indicator (RSSI), an MBSFNsignal-to-noise ratio (SNR), a reference signal received power (RSRP) ofan MBSFN signal, an MBSFN reference signal received quality (RSRQ) and ablock error rate (BLER).
 8. The method of claim 7, wherein the MBMSmeasurement configuration configures the MBMS measurement result in formof metrics comprising at least one of the E-UTRA carrier MBSFN RSSI, theMBSFN SNR, the RSRP of the MBSFN signal, the MBSFN RSRQ and the BLER. 9.The method of claim 4, further comprising: stopping performing the MBMSmeasurement for the MBSFN area, when the UE stops receiving the MBMSservice belonging to the MBSFN area transmitted by MBSFN transmission orchanges to receive the MBMS service belonging to the MBSFN areatransmitted by a unicast.
 10. The method of claim 4, where the step ofperforming the MBMS measurement for the MBSFN area further comprises:performing the MBMS measurement by measuring at least one MBSFN subframeallocated to the MBSFN area identified by the MBSFN area ID, whereinmeasuring the at least one MBSFN subframe allocated to the MBSFN areacomprises measuring a reference signal in the at least one MBSFNsubframe.
 11. A method of handling a multimedia broadcast multicastservice (MBMS) minimization of driver test (MDT) for a user equipment(UE) of a wireless communication system, the method comprising:receiving an MBMS measurement configuration which instructs the UE toperform an MBMS MDT operation, from a first network of the wirelesscommunication system; performing the MBMS MDT operation for amulticast-broadcast single frequency network (MBSFN) area where the UEis receiving an MBMS service via MBSFN transmission, in response toreception of the MBMS measurement configuration; transmitting an MBMSmeasurement result generated by performing the MBMS MDT operation and anMBSFN area identity (ID) to a network of the wireless communicationsystem, wherein the network is the first network or a second network ofthe wireless communication system; and transmitting a notification tothe first network for notifying that the UE has the stored MBMSmeasurement result for the MBSFN area identified by the MBSFN area ID.12. The method of claim 11, wherein the MBMS measurement configurationtransmitted from the first network comprises the MBSFN area ID.
 13. Themethod of claim 11, wherein the step of performing the MBMS MDToperation for the MBSFN area in response to reception of the MBMSmeasurement configuration comprises: performing an MBMS measurement forthe MBSFN area; and storing the MBMS measurement result for the MBSFNarea.
 14. The method of claim 13, further comprising: stoppingperforming the MBMS measurement for the MBSFN area, when the UE stopsreceiving the MBMS service belonging to the MBSFN area via MBSFNtransmission or changes to receive the MBMS service by a unicast. 15.The method of claim 13, where the step of performing the MBMSmeasurement for the MBSFN area further comprises: performing the MBMSmeasurement by measuring at least one MBSFN subframe allocated to theMBSFN area identified by the MBSFN area ID, wherein measuring the atleast one MBSFN subframe allocated to the MBSFN area comprises measuringa reference signal in the at least one MBSFN subframe.
 16. The method ofclaim 11, wherein the MBMS measurement configuration is sent to the UEby the first network after the first network receives capabilityinformation indicating that the UE supports an MBMS measurementcapability from the UE.